The peat fire in Cyberpark could have started from an illegal immigrants' settlement which has its own basic sewerage system and a kitchen.
Fire and Rescue Services Department public relations officer K. Kobala said while the department was looking at other possibilities, such as natural ignition of fire due to intense heat, the main factor was most likely indiscriminate open burning or cooking by the illegal settlers.
Pictures complied in the Ops Gambut report showed cooking utensils scattered on the ground near their huts and "toilet".
On the progress of Ops Gambut, he said the department was optimistic that the fire would be totally extinguished in two days' time.
Until today, about 1.2 hectares of the peat soil in the area was still burning.
Since the fire broke out on Aug 1, the 51-member team from seven fire stations had managed to douse 2.8 hectares of the peat fire.